Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!caen!mtu.edu!mtu.edu!cdh From: cdh@mtu.edu (Chris Hooper) Newsgroups: comp.sys.amiga.hardware Subject: Help! My 2000 motherboard is dead Keywords: dead motherboard megachip Message-ID: <1991May13.031522.28822@mtu.edu> Date: 13 May 91 03:15:22 GMT Sender: news@mtu.edu Reply-To: cdh@mtu.edu (Chris Hooper) Distribution: usa Organization: Michigan Technological University Lines: 140 Yes, this is a repost. Since I received zero words of advice my first time around, I'm hoping someone will have something to say (flame or not) that might help me with my situation. I'm getting desperate quick :) My Amiga is dead. Machine: Amiga 2000, AmigaDOS 1.3 in ROM, Rev 4.3 motherboard 1M Agnes, Supra 8-up (with 2M), IVS Trumpcard Problem/Symptoms: A diode was burned out on the motherboard (actually burned clean through). It was replaced (1N4001) located near the power supply connector to the motherboard. A technician at the company that sells the Megachip said diaode D400 is on the +12 power input. He then told me that the particular revision motherboard I have (B2000 Rev 4.3) is missing a capacitor (C908) which is needed for the Megachip board to work. He stated this capacitor is listed as 100pf, but recommeded 70pf. I still have yet to put this capacitor in. My machine refuses to boot. White screen on power up (with *no* boards in machine, no floppy in drive). Goes through gray colors, but when it should come up with a work bench prompt, stays white instead. Floppy drive clicks like it is waiting for a disk. When disk is inserted, floppy stops clicking, however, access light does not come on drive and drive does not spin. Pull the disk out and the drive starts clicking again. With the Trumpcard in, the machine will attempt to Autoboot off the hard drive. It usually does not succeed. The background color *does* change from white to blue (which is my default background color). Three out of the many powerup attempts let to a screen of garbage (kinda looked like a page zero), with moving bits on the screen. Once or twice the machine actually booted to the point where I could type a command and it would access the disk (could not see what I typed still). The machine usually died pretty quickly. Most of my attempts at booting, however, ended up with the machine just stopping completely before it finished booting. By stopping, I mean no activity; CPU halted or waiting for something. We tried using a logic probe, but everything looked "normal" as far as we could tell. ie: yup, there was power to memory, chips, etc. Ok, I'm a CS major (with enough electrical experience to be dangerous) and my friend is a EE (both undergrads). Since it goes through its power-up colors and booted (kinda) a couple time, I assume the 68000 is running fine. Because the floppy drive is also acting up, I am guessing it might have to do with a chip around Gary that also has a hand in chip memory access (maybe two chips are bad??) Suspected Killers: Megachip 2000 (The board for about $350 which allows you to put a 2M Agnes in the 2000) Supra 8-up (Either the Megachip, or the Megachip in combination with this board) How it happened (I think): The roommate purchased this board originally for his machine, but had to send his motherboard in for replacement since it was a revision 6 and would not work with the Megachip. While his machine was gone, I became interested in possibly having a 2M board in my machine :) So: I pulled my machine completely apart (motherboard too) so I could get that darn original Agnes out of its socket. I had to use the holes on the bottom as well as the chip puller to pry that sucker from its wedge. Thinking back, I really had to torque on the chip socket to get it out. Its highly possible that I damaged the Agnes socket while pulling the chip. I am leaning toward that idea now. I put the new Agnes board in, and put the machine all back together. It worked beautifully (2M chip, 2M fast - Supra) for about an hour. I then began to notice a flash occasionally. At first I thought it might be power or the monitor acting up (dorms). The longer I left the machine on, the worse the flicker got. If I powered my Amiga off, then back on the flicker would go away for a while, but always return faster than previously. I pulled the Supra and Trumpcard out and the problem went away. I then put the Trumpcard back in and the problem still did not return. I assume there must have been some conflict between the Supra and the Megachip. I let the machine run for a whole day without the Supra board and it did not give incident. I then put the Supra back in. The problem did not come back immediately. Then I did the foolish thing. I turned the monitor off and let the machine sit for a day (I usually leave my machine on 24 hours a day). When I came back the next day, the screen was blank (border color). I cycled power and the machine came back on for a few seconds and then quit. I tried again; same result. My Amiga has been unusable since. At this point, I pulled my machine all apart and removed the Megachip. I replaced the original Agnes back into its socket. When I reassembled the machine, the screen did not return! I tried pulling and reinserting Agnes; to no avail. Over the next few days, I had the opportunity to try another 1M Agnes and also a 512K Agnes. Each produced exactly the same results. What I have already tried: Replacing the diode that was burned clean through. Swapping every pullable chip on the motherboard [68000, Agnes, Paula, Denise, Gary, ROM, the two 8520 chips, etc]. Probing around randomly with a logic probe. Praying to the Magic Montra Sacrificing the neighbor's cat. (Just kidding, all you animal lovers out there) Anyone with any ideas or suggestions, please help. Thanks. -Chris - Chris Hooper Computing Technology Services Consultant cdh@mtu.edu Michigan Technological University Also: cdh@mtus5.mtu.edu CDH@MTUS5.Bitnet and cdhooper@symmetry.cs.mtu.edu